Circuit breaker



A11g- 19, 1958 w. H. MIDDENDORF 2,848,577

CIRCUIT BREAKER Filed Aug, 2, 1956 2 Sheets-Sheet 1 A118- 19,'1953 w. H. MIDDENDORF I2,848,577

CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed Aug. 2, 1956 if/mf ATTORA/EYS.

William H. Middendorf, Covington, Ky., assigner to rEhe Wadsworth Electric Manufacturing Company, line., Qovington, Ky., a corporation of Kentucky Application August 2, i956, Seriai No. dhlfii llS Ciainis. (Cl. 26d-33) This invention relates to circuit `breakers and is more particularly directed to circuit breakers of the type including magnetically responsive means for tripping the breaker upon the occurrence of a heavy overload, or short circuit condition, and thermally responsive means for tripping the breaker upon the occurrence of a persistent overloadcurrent of lesser magnitude.

In general, a circuit breaker of the type with which the present invention is concerned, comprises a pair of contacts, a spring actuating mechanism for opening and closing the contacts, and a current responsive tripping mechanism for releasably latching the operating mechanism. The tripping mechanism functions to release the operating mechanism immediately upon the occurrence of a heavy current overload, or after a predetermined interval in response to a continued moderate current overload.

One form of tripping mechanism includes a thermal element which is heated by excessive current ow and bends to shift a latching member and disengage it from a cooperating element of the operating mechanism. The tripping means also includes a magnetically responsive member which is energized by any large current surge through the breaker and is adapted to shift the latching surface and release the operating mechanism.

In previously proposed circuit breakers, the thermal element is in the form of an elongated bimetaliic strip; while the magnetic release means includes a core mounted on the free end of the bimetallic strip and an armature spaced from the core and adapted to attract the core in the presence of a strong magnetic field produced by a current surge through the breaker. In these prior devices the magnetic core and bimetallic strip move in the same direction to shift the latching surface and effect release of the operating mechanism. This requires that the magnetic core ilex the bimetallic strip during high current overloads. T he force necessary to bend the `bimetallic strip places a substantial additional burden upon the magnetic tripping mechanism; moreover, this burden increases rapidly as the current rating of the breaker increases. Thus for example, the bimetallic strip used in a typical 103 ampere circuit breaker has ldimensions of the order of .062 x .5 x L. Several pounds of force are required to move the free end o-f this strip a suicient distance to effect release of the operating mechanism. As a result, the circuit breaker docs not open immediately except in the case of exceedingly high overload currents creating powerful magnetic fields. It will be appreciated that in many installations it is desirable to provide immediate opening of the breaker contacts at a lesser overload current not effective to produce such a strong magnetic field.

A tripping mechanism of the construction described above has the further disadvantage that thc bimetallic strip must be flexed in order to reset the circuit breaker following tripping. This is highly undesirable since flexing the bimetal during resetting, subjects it to strains 84,57? Patented Aug. i9, i958 that tend to cause a change of calibration, as a result of which the breaker no longer operates at the desired overload current.

The present invention is predicated upon the concept of providing a circuit breaker including a thermally responsive element which moves in one direction to release the operating mechanism upon the occurrence of a continued moderate overload; and a magnetic element which moves in a different direction to effect rapid release of the operating mechanism in response to the occurrence of a high overload.

More specifically, one preferred form of circuit breaker constructed in accordance with the present invention comprises a spring actuated contacting operating mechanism, and a tripping mechanism including an elongated bimetallic strip which thermally flexes in one direction to release the operating mechanism and carries a magnetic core which is adapted to be shifted transverse to the plane of flexure of the bimetallic strip to effect magnetic release of the operating mechanism.

ln accordance with the present invention the bimetallic strip is not rigidly mounted in the `breaker housing but rather is mounted upon a movable support plate. The support plate is spring urged against suitable abutment elements positioned and configurated so that the support plate holds the foot end of the bimetallic strip stationary during bending of the strip under thermal stresses, but pivots in a plane transverse to the path of bimetallic flexure when the magnetic core is energized.

In the preferred embodiment, the magnetically responsive core carries a latching surface extending beyond the core and adapted for cooperative engagement with the operating mechanism. This core is mounted on the free end of the bimetallic strip and is disposed for cooperation with a magnetically responsive armature mounted relative to the core so that the core is moved at right angles to the plane of iiexure to the bimetallic strip when the core is energized by a heavy overload current. When the core is shifted in a transverse direction, the bimetallic Strip and support plate pivot in a transverse plane. This movement causes the latching surface to `become disengaged from the cooperating member of the operating mechanism in a direction at right angles to the direction the latching surface is shifted due to the thermal action of the bimetallic strip.

One of the principal advantages of the present construction is that the bimetallic strip is not flexed during movement of magnetic tripping elements so that even a heavy duty circuit breaker requires but a minimum magnetic force to trip the operating mechanism. rl`his facilitates the provision of a circuit breaker in which the contacts are rapidly opened at a substantially smaller overload current than was previously practicable.

A further advantage of the present invention is that the bimetallic strip is not iiexed during resetting of the breaker contacts. As explained in detail below, the latching surface on the core cooperates with a member of the operating mechanism during the resetting operation so that the bimetallic strip and support plate pivot laterally during resetting to effect relatching. There is no tendency of the bimetallic strip to flex outwardly during the resetting operation, and it is subjected to no distorting forces which might change its calibration.

A further advantage of the present invention is that the thermal and magnetic tripping means of the breaker function completely independently of one another; so that, as explained below, each of these tripping means can be individually calibrated. Thus the circuit breaker can be selectively rendered more or less sensitive to either high or low overload conditions without affecting the calibration of the tripping means controlling the other condition A further advantage of the present circuit breaker construction is that it greatly facilitates accurate calibration, particularly of the thermally responsive tripping means. In the past, it has been necessary to calibrate each circuit breaker individually by adjusting the Calibrating mechanism until the breaker tripped at the desired overload current. l have determined that this difficulty is due to the fact that the calibration obtained varied withV the thickness of the metal components of a breaker and that under normal production conditions it was impractical to control the dimensions of such components to provide uniform calibration. In contrast the present Calibrating means is independent of the thickness of any metal part and depends upon dimensions which can readily be maintained. Consequently, uniform calibration can be obtained by making the same adjustment on each circuit breaker which greatly expedites the Calibrating operation.

A further advantage of the present circuit breaker is that the Calibrating means does not place appreciable strain on the housing or other parts, so that the housing does not tend to crack or break during calibration or during subsequent operation.

An additional advantage of the present circuit breaker is that it can be economically manufactured. The present circuit breaker is of relatively simple construction and is adapted to provide long periods of trouble free use.

These and other objectives and advantages of the present invention will be more readily apparent from a further consideration of the following detailed description of the drawings illustrating a preferred embodiment of the invention.

In the drawings:

Figure l is a vertical elevational view of a circuit breaker with the front housing plate removed;

Figure 2 is an enlarged elevational view of the tripping and operating mechanism;

Figure 3 is a cross sectional view taken along line 3-3 of Figure 1, showing the carrier in a latched position;

Figure 4 is a Cross sectional view similar to Figure 3, showing the manner in which the carrier is released by action of the magnetic core and'armature;

Figure 5 is a cross sectional view similar to Figure 3 of a modified form of core and armature;

Figure 6 is a cross sectional view similar to Figure 3 of another form of core and armature;

Figure 7 is a perspective view partially in section of the magnetic core shown in Figures 1-4;

Figure 8 is a bottom elevational view of the bi-metal support plate and spring mount; and

Figure 9 is a cross sectional view taken along line 9-9 of Figure 1.

One preferred form of circuit breaker constructed in accordance with the present invention is shown in Figures 1 through 4. As there shown, a circuit breaker 10 comprises a housing 11 formed of two mating sections 12 and .l

13 constructed of molded insulating material such as Bakelite or the like. The housing encloses a stationary contact 14, a movable contact 15, an operating mechanism 16 for shifting the movable Contact into and out of engagement with the stationary contact, and a latching mechanism 17 for releasably holding the operating mechanism.

The stationary Contact 14 is welded or otherwise rigidly secured to a conducting strip 18. This strip, which is of an irregular coniiguration, is seated in a multiple angular slot provided in the housing and is secured at its outer end to terminal connecting means 20, preferably in the form of two spaced outwardly extending Contact jaws 21. The jaws are adapted to receive a Contact blade or other conductive element and are spring urged into Contact with such an element by means of a U-shaped spring clip 22. At the opposite end of the housing 11 is a terminal 23 including a screw 24 threadably engaging an opening in arm 25 of conductor strip 26. This strip includes a leg 2'7 rigidly supported in a suitable groove formed in the housing walls. Leg 27 is provided with a threaded openformed in the under surface of plate 43.

l ing 28 adapted to receive Calibrating screw 30, the function of which is explained in detail below.

Movable contact 1S is welded or otherwise rigidly secured to the free end of switch arm 31. This switch arm is provided with two legs 32 disposed at its upper end, the legs being pivotally supported in recesses 33 formed in carrier member 34. Switch arm 31 and carrier 34 constitute two elements of operating mechanism 16 for shifting the movable Contact between an open and closed position. Carrier member 34 includes two spaced parallel arms 35 and 36 joined by a cross strip 37. The arms are provided with aligned openings for receiving a pin 33 which extends across the housing and is journaled in suitable openings provided in the opposite housing sections.

In addition to switch arm 31 and carrier 34, operating mechanism 16 includes an operating lever 50, a main operating spring 41, a handle 42 and a plate 43 integral with the handle. Operating lever Alti is mounted adjacent to wall 11 of the housing between that wall and carrier 34. The lower end of this lever is pivotally supported by an arcuate shoulder 44 provided in the housing wall. The upper end of the lever is received within a recess 45 The plate is adapted for reciprocating movement within the housing and is guided in its movement by guideways 46 formed in the housing walls. Handle 42, formed integrally with the plate, extends outwardly through an opening 47 formed in the front face of the housing and provides a ready means for shifting the plate and operating lever. The upper end of the operating lever is provided with a tang 48 adapted to engage one end of the spring 41, the other end of the spring being secured to the upper end of switch arm 31 in any suitable manner, as by passing the end of the spring through a suitable opening Sti formed in that arm. It will be appreciated that spring l1 functions as an over center spring effective to urge switch arm 31 to an open or closed position depending upon the position of the operating lever and carrier.

One of the arms 36 of carrier member 34- is provided with an extension 51 adapted to function as a release arm. This release arm includes a transversely extending flange 52 adapted for engagement with latching finger 53 of magnetic core 54, as explained below. This same arm of the carrier also includes a lug S5 adapted for cooperative engagement with operating lever 40, so that the operating lever is effective to shift the carrier member during manual closing of the contacts as explained below.

Tripping mechanism 16 comprises, in addition to magnetic core 54, an elongated bi-metallic strip 56 including a foot S7 which is welded or otherwise secured to a support member 5S. ln the embodiment shown, support member S3 is in the form of an elongated plate having upturned arm 60 formed on the outer end thereof This arm is provided with a groove, preferably ldisposed centrally of the arm for receiving the tip 61 of Calibrating screw 30. The undersurface of support member 58 is provided with a longitudinal groove 62 and a transverse groove 63. These grooves function to accurately position the point at which the floating support member is engaged by mounting spring 64. This coil spring is compressed between support member 5S and a bottom wall 65 of the breaker housing. The end of mounting spring 64 in engagement with plate 58 includes a segment 66 extending diametrically across the spring and a portion 67 extending at right angles to segment 66. Segment 67 of the spring also preferably extends slightly upwardly in the direction of the axis of the spring, for the reasons explained below.

in its assembled position, diametral segment 66 resides in engagement with longitudinal groove 62 of the support member; and endwise portion 67 of the spring resides in engagement with the portion of transverse groove 63 which is remote from the release arm of carrier 34. The end of support member 58 remote from the calibration.

screw is forced by the spring into engagement with abutments 68, 68 respectively `formed on housing members 12 and 13. Abutment member 68 is shown by dotted lines and is preferably provided with a flat horizontal face which extends outwardly from housing section 12 to a point substantially in alignment with the end of calibrating screw 3f). Abutmcnt member 68 differs from abutment 68 only in that its lower surface is below that of abutment 68. This difference in the lower surfaces permits unhampered sideways rotation of support member 58 about its longitudinal axis. Longitudinal sliding movement of the support plate is prevented in one direction by engagement of arm 60 with the conical tip of calibrating screw 30. In the other direction, sliding movement of plate 58 is restrained by the engagement of the end of bi-metallic strip 56 with abutment member 63. The end of the bimetallic strip is preferably rounded to facilitate pivotal movement of plate 58 about the abutment member.

The free end of bi-metallic strip 56 carries magnetic core 54. This core, formed of ferro magnetic material, is generally U-shaped and includes a support arm 70, a second arm 71 extending parallel to support arm 70 and being appreciably shorter than that arm and a connecting segment 72. The connecting segment is welded or otherwise permanently secured to the surface of the bimetallic strip facing carrier member 34. Support arm 70 is provided with a slot 73 adapted to receive a narrow band 74 formed on armature 75. Armature 75, also formed of magnetically permeable material, is of generally right angular configuration and includes a wall engaging pivot arm 76 and a segment 77 adapted to be yattracted to the core. Arm 76 and segment 77 are joined by band '74 which is loosely received within aperture 73 in the support arm of core member 54. The relative sizes of band '74 and aperture 73 are such as to permit pivotal movement of the armature relative to the core.

ln normal operation, pivot arm 76 of the armature is disposed closely adjacent to the inner wall of section 13 of the housing; and extends substantially parallel there to as best shown in Figure 3. However, as explained below, when core Sli is energized, arm 71 of the core attracts segment 77 of the amature, causing it to close air gap 78. This causes the armature to pivot about the end of arm 76 in engagement with the housing and in turn forces the core and. upper end of the bi-metallic strip to shift transversely of the housing. This latter movement is effected by rotation of the support 58 about its longitudinal axis. Transverse pivotal movement of plate 58 and bi-rnetallic strip 56 are resisted by segment 67 of support spring 64 which exerts a small torsional force on the bottom of the plate.

Core 54 also includes a latching finger 53 extending outwardly from the undersurface of connecting segment 72 of the core toward the carrier member. This finger is adapted to reside in notch 8f3 formed on the outer end of the release arm, the notch having shoulder E1 etlective to limit the amount finger 53 extends over the release arm.

When the contacts are closed, current flows through the circuit breaker from jaws 21, through conductor strip 18, across contacts 14 and 15, through switch arm 31, and flexible conductor 83 welded to the switch arm, to `bi-metallic strip 56, the current then passes through bimetallic strip 56, plate S8, flexible conductor 82 and conductor strip 27 to terminal 23.

When the circuit breaker is installed in a circuit, contact 15 is manually shifted from the open to the closed position by actuating handle 42. ln order to close the contacts, the operating handle is shifted from its left hand position shown in Figure l to a position at the right hand end of the slot. During its movement, handle 42 causes operating lever 4t) to pivot clockwise about shoulder 44. The operating lever in turn carries the upper end of spring 41 in a clockwise direction. The operating lever during its pivotl movement also engages projecting lug 55 formed on arm 36 of the carrier member and thereby forces the carrier member to rotate clockwise about transverse pin 38. Near the end of its clockwise movements, flange 52 of release arm 51 engages latching finger 53, of the core. As best shown in Figure 9, the outer end of flange 52 is of arcuate configuration to provide a camming surface which forces the core and the upper end of bi-metallic strip 56 to move in a transverse direction. This causes support member gft to pivot on its longitudinal axis about Calibrating screw 3ft and abutment member 68. As the operating handle nears its extreme right hand position, finger 53 is forced outwardly beyond flange 52 and as carrier member 34 is pivoted downwardly an additional amount, the linger slides into notch in flange 52. The finger is urged into the slot under the influence of segment 67 of mounting spring 64 which urges plate 5S to rotate in a direction effective to force the core towards wall 13. It should be noted that during the latching of the carrier member bimetallic strip 56 is not flexed in any way.

After the carrier member is latched, the operating handle is then returned to its left hand position shown in Figure l to effect manual closing of movable contact 15. Movement of the handle in this direction causes counterclockwise pivotal movement of operating lever di) and causes counterclockwise movement of over center spring 41 secured to the lever. As the operating handle approaches its extreme left hand position, the spring is moved beyond its over center position forcing switch arm 31 in a clockwise direction about its pivot points in recesses 33 of the carrier member. Moveable Contact l5 is thus brought intoengagement with stationary contact 14.

The tripping mechanism releasably holds carrier 34 in its position with contacts `and 15 closed until the occurrence of an overload condition. Tripping mechanism 17 is adapted to release carrier 34 in the event of a continuing overload of moderate magnitude by means of thermally responsive bi-metallic strip 56. The breaker is also effective in response to a heavy overload, that is one of an order of magnitude several times that of the rated capacity of the breaker, to immediately release the carrier through magnetically responsive means including core 54 and armature 75.

More particularly, upon the occurrence of a moderate current overload of continuing magnitude, bi-metallic strip 56 becomes heated and since the high expansion side of the element is disposed toward the carrier member, the free end of the bi-metallic strip deflects away from the carrier, to the right as shown in Figure 2. lf the moderate overload continues for a sufficient period of time, the free end of the bi-metallic element is shifted to the right a suicient distance to disenage latching finger 53 of the core from flange 52 of the carrier member. As soon as the carrier member is released from engagement with the core, it is urged counterclockwise by main operating spring 41. Movement of the carrier member in this direction shifts the upper end of switch arm 31, which is pivoted in recesses 33 of the carrier member, to a position in which spring 41 is shifted beyond an over center position causing rapid counterclockwisc rotation of switch arm 31 separating contact 1S from stationary contact 14.

When a short circuit, or heavy overload condition, causes a current flow of more than a predetermined magnitude through the breaker, the current in flexible conductor 53 and bi-metallic strip 56 energizes core member 54 causing the establishment of a strong magnetic field around the core. The effect of this magnetic field is to cause the attraction of free end 84 of armature 75 to arm 7l of the core. As the free end of the armature moves toward the core, the armature pivots about aperture 73 in support arm 7) of the core. This movement forces pivot arm 76 of the armature against the inner surface of base wall 13 of the housing which in turn forces the core away from the housing wall to the position shown in Figure 4. Movement of the core in this direction is accomplished without bending the bi-metal since the foot of the bi-metal pivots with support plate 53, that plate turning about its longitudinal axis between calibrating screw 3ft and abutment member 63. Before core 54 reaches its extreme unlatching position shown in Figure 4, linger S3 slides off the end of flange 52, thereby releasing arm 5l and freeing the carrier for counterclockwise movement as explained above. The operating mechanism is thus tripped to open contacts l5 and 14 in the same manner as before.

It will be noted that while support spring 64 exerts a restoring force upon support strip 58 tending to rotate the bi-metallic strip and core toward base wall 13, the restoring force exerted by this spring is not sufficient to impede rapid tripping of the release arm when a sufiici* ently large current flows to energize core 54. Also, it is to be understood that the upward component of force exerted by spring 64 along center groove 63 of plate 5S is of sufficient magnitude to hold the plate firmly against Calibrating screw 36 and abutment 68, throughout the operation of the device including flexing of bi'metallic strip 56.

Two separate Calibrating means are provided in the breaker, one for Calibrating the thermally responsive` element and one for Calibrating the magnetically responsive element. These two Calibrating means function completely independently of one another and the adjustment of one in no way affects the adjustment, or setting of the other. More specifically, Calibrating screw 3d provides means for adjusting the thermally responsive means of the breaker. By threading this screw in and out relative to arm 60 of plate S, this end of the plate is raised or lowered as the plate shifts on a transverse axis about abutment 68. Adjustment of the angulation of the plate in turn causes the bi-metallic strip to move in its plane of expansion so that the amount that linger 53 extends over flange 52 is readilycontrolled. Obviously, if the core is positioned so that when the lai-metallic strip is cold, this finger extends only part way over the flange, the finger will become disengaged from the flange when the bi-metallic element has moved a shorter distance than would be the case if the flange were initially positioned to extend a substantial distance over the finger. lt will be appreciated that the lcalibration of the thermally responsive element depends upon the taper of screw 36, the size of groove in arm 60, and o-ther dimensions which can be controlled accurately. Consequently, a number j of breakers can be uniformly calibrated by making the same number of turns in screw 30.

Separate means in the form of an adjustable abutment element such as set screw S5 are provided for Calibrating the magnetically responsive release mechanism. shown in Figures 3 and 4, screw 85 threadably engages a suitable opening provided in base wall 13 and is disposed for abutment with support arm 7th of core 54. This set screw is effective to shift the core perpendicular to the path of bi-metallic strip movement inwardly and outt3" wardly relative to flange 52. As the magnetic core is shifted, armature '75 assumes a position in which a greater or lesser air gap 7? is established between the armature and core. As this air gap is decreased, the magnetic flux set up by a given current increases. As best shown in Figure 3, the air gap is decreased when this core is shifted away from housing section i3. Decreasing the air gap increases the magnetic force and lessens the distance finger S3 must move to release flange 52 thereby reducing the tripping time of the breaker at high overloads.

The details of a preferred form of core are best dis closed in Figure 7. As there shown, core 54 is formed by overfolding a strip of magnetically permeable material upon itself to form a length of material of double As l wall thickness including layers 86 and 87. Inner layer 86 is provided with an extending tab which is bent outwardly beneath the under surface of outer section 87 to form finger 53. Opening 73 is then punched or cut from one end of the core strip. Finally, the core is bent into a U-shaped configuration to form the support wall 70, shorter wall 71, and connecting section 72. This particular form of core is advantageous for several reasons. In the first place, it facilitates the manufacture of a core having a latching surface of the type utilized in the present breaker. Additionally however, the core is effective to provide a maximum effective flux for tripping the breaker, thereby providing an extremely rapid trip time under heavy overload conditions. The lamination of the core formed by overfolding the core strip minimizes eddy currents which are normally produced by the magnetic flux and tend to set up counter flux which reduces the effectiveness of the tripping flux.

Modified forms of core and armature constructions are shown in Figures 5 and 6. It is to be understood that each of the cores 88 and 90 is mounted on the free end of a bi-metallic strip 56 having a foot supported on a floating mounting plate as explained above. Each of the cores is configurated to form a latching finger S3 adapted for engagement with a flange 52 provided on a carrier member 34, the carrier member forming part of an operating mechanism of the type described above.

ln the embodiment shown in Figure 5, bi-metallic strip 56 is adapted to flex to the right to effect release of the carrier member upon the occurrence of a continued moderate overload. Magnetic core 88 is generally U-shaped having a first arm 91 welded or otherwise secured to the bi-metallic strip and a second arm 92 extending parallel to the first. Each of the arms is provided with an outwardly extending flange 93 adapted to cooperate with a stationary armature 94 formed of magnetically permeable material and permanently mounted in a groove 95 provided in housing wall 12. In the presence of an overload or short circuit condition the large current flowing through the bi-metallic strip and flexible conductor 83 energizes core 88, forming a strong magnetic field across gap 96 between the core and armature. The core is thus forced toward the armature in a direction perpendicular to the plane of flexing of the bi-metal to disengage finger 53 from flange 52 to effect release of the operating mechanism.

In a further modification shown in Figure 6, core 90 is mounted upo-n the free end of `a bi-metallic strip 56 which is constructed so that it llexes to the right when heated, to thereby release the carrier member in the event of Ia continued moderate overload. The bi-metallic member is mounted upon a floating support in the same manner as the bi-metallic strip in Figure l. Core 90 is formed of a substantially U-shaped strip of magneti cally permeable material and includes a support arm 97, a second arm 98 parallel to the support arm and appreciably shorter than that arm, and a connecting segment 100 joining arms 97 and 98. Support arm 97 is provided with an opening lill for loosely receiving a tang 102 formed on the end of magnetically permeable armature lr03. The free end of armature 103 resides in a slot provided in housing wall l2 4and is restrained from movement across air gap i041 between the armature and core arm 98 by a shoulder 105 formed in the breaker wall.

" When the breaker in Figure 6 is subjected to a heavy current overload, energizing core EN), the core tends to close air gap 104. Thus, in the presence of the magnetic field core 90 is shifted toward wall 12, disengaging finger 53 from the flange 52 of carrier member 34. This effects a release of carrier member 34 and a tripping of the operating mechanism which opens contact 15.

It will be appreciated that in each of the embodiments shown and described above the core, when energized by a heavy current is forced in a direction at an angle to the plane of flexure of the bi-metallic strip. Also, while not described in detail, it is to be understood that during closure of the breaker contacts, the latching fingers on modied cores SS and 9@ engage and cooperate with the Harige 52 on the carrier member to releasably latch the carrier member without bending the timetable strip as explained in detail in connection with the embodiment shown in Figures l-4.

Having described my invention I claim:

l. A circuit breaker comprising a housing, relatively movable contacts disposed within said housing, spring urged operating means for opening said contacts, current responsive tripping means effective to releasably latch said operating means and to release said operating means in response to an overload current, said tripping means comprising a thermally responsive bimetallic strip adapted to flex in a first plane and thereby cause release of said operating means, and a magnetic means including a magnetically permeable member carried by said bimetallic strip and effective to cause movement of said bimetallic strip in a second plane and thereby effect release of said operating means,

2. A circuit breaker comprising a housing, relatively movable contacts disposed Within said housing, spring urged operating means for opening said contacts, current responsive tripping means effective to releasably latch said operating means `and to release said operating means in response to an overload current, said tripping means comprising a latching surface disposed for engagement with a cooperating element of said operating means, a thermal current responsive element adapted to shift said latching surface in one direction to release said operating mechanism and a magnetic current responsive element adapted to shift said latching surface in a different direction to release said operating means.

3. A circuit breaker comprising a housing, relatively movable contacts disposed Within said housing, spring urged operating means for opening said contacts, current responsive tripping means effective to releasably latch said operating means and to release said operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a yieldable support member, one end of said bimetallic strip being mounted on said support member, a magnetic core mounted on the free end of the bimetallic strip, a latchingr surface carried by the free end of the bimetallic strip and adapted for engagement with a cooperating element of the operating means, a magnetic armature disposed adjacent to and in normally spaced relationship from a portion of said core, said bimetallic strip being adapted upon flexing to shift said latching surface in one direction to release said operating means, the magnetic core and armature cooperating when energized to shift the latching surface in a direction transverse to the direction of bimetal movement to effect release of the operating means.

4. A circuit breaker comprising a housing, relatively movable contacts disposed within said housing, spring urged operating means for opening said contacts, current responsive tripping means eifective to releasably latch said operating means and to release said operating means in response to an overload current, said tripping means comprising a thermally responsive bimetallic strip adapted upon liexing to cause release of said operating means, and a magnetic means including a magnetically permeable member carried by said bimetallic strip and effective to release said operating means yby movement in a direction perpendicular to the direction of bimetallic flexlng.

5. A circuit breaker comprising a housing, relatively movable contacts disposed Within said housing, spring urged operating means for opening said contacts, current responsive tripping means effective to releasably latch said operating means and to release said operating means in response to an overload current, said tripping means comprising a latching surface disposed forengagement with a cooperating element of said operating means, a

il@ thermal element adapted to shift said latching surface in a rst direction to release said operating mechanism, and a magnetic element adapted to shift said latching surface in a direction perpendicular to the iirst direction to release said operating means.

6. A circuit breaker comprising a housing, relatively movable contacts within said housing, spring urged operating means for opening said contacts, current responsive tripping means eifective to releasably latch said operating means and to release said operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a support member, one end of said bimetallic strip being mounted on said support member, said support member being mounted for pivotal movement in a plane transverse to the plane of bimetal iiexure, a magnetic core mounted on the free end of the bimetallic strip, a latching surface carried by the bimetallic strip and adapted for engagement with a cooperating element of the operating means, a magnetic armature clisposed -adjacent to and in normally spaced relationship from a portion of said core, said bimetallic strip being adapted upon flexing to shift said latching surface to release said operating means, the magnetic core and armature cooperating when energized to pivot the bimetallic strip and support member in a plane transverse to the plane of bimetallic fleXure to effect release of the operating means.

7. A circuit breaker comprising a housing, relatively movable contacts disposed within said housing, spring urged operating means for opening and closing said contacts, current responsive tripping means effective to releasably latch said operating means and to release said operating means in response to an overload current, said tripping means comprising a latching surface disposed for engagement with a cooperating element of said operating means, a thermal current responsive element adapted to shift said latching surface in one plane to release said operating mechanism, and a magnetic current responsive element adapted to shift said latching surface in a second plane to release said operating means, said cooperating element of the operating means being effective to shift the latching surface in the second plane to effect relatching of the operating mechanism following release thereof.

8. A circuit breaker comprising a housing, relatively movable contacts disposed within said housing, spring urged operating means for opening and closing said contacts, current responsive tripping means effective to releasably latch said operating means and to release said operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a support member, said support member being mounted for pivotal movement in a plane transverse to the plane of bimetal iiexure, one end of said bimetallic strip being mounted on said support member, a magnetic core mounted on the free end of the `bimetallic strip, a latching surface carried by the bimetallic strip and adapted for engagement with a cooperating element of the operating means, a magnetic armature disposed adjacent to and in normally spaced relationship from a portion of said core, said bimetallic strip being adapted upon flexing to shift said latching surface in the direction of bimetal flexure to release said operating means, the magnetic core and armature cooperating when energized to shift the latching surface in a direction transverse to the direction of bimetal flexure to effect release of the operating means, said operating means being effective to pivot the bimetallic strip and support member in a direction transverse to the plane of bimetal iiexure to relatch the operating mechanism following release thereof.

9. A circuit breaker comprising a housing, relatively movable contacts disposed within said housing, spring urged operating means for opening said contacts, current responsive tripping means effective to releasably latch said operating means and to release said operating means in response to an overload current, said tripping means comprising a thermally responsive bimetallic strip adapted upon flexing to cause release of said operating means, and a magnetic means including a magnetically permeable member carried by said bimetallic strip and effective to release said operating means by movement in a direction transverse to the direction of bimetallic flexure, first means for effecting thermal calibration of Said circuit breaker comprising a movable abutment member for adjustably positioning said bimetallic strip in its plane of fieXure, and second means for effecting magnetic calibration of said circuit breaker comprising a second movable abutment member for adjustably positioning said bi metallic strip in a plane transverse to the plane of bimetallic flexure.

l0. In a circuit breaker comprising a housing, movable contacts disposed within the housing, and spring urged operating means for opening and closing said contacts, the improvement which comprises current responsive tripping means effective to releasably latch the operating means and to release the operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a support mem-ber, one end of said bimetallic strip being mounted upon said support member, a compression spring engaging the opposite side of said support member from said bimetallic strip, stationary abutment members in engagement with said.

support member, said abutment members and spring cooperating to hold said support member stationary during exure of said bimetallic strip but permitting pivotal movement of said support member in a plane transverse to the plane of flexure of said bimetallic strip, a magnetic core mounted on the free end of the bimetallic strip, a latching surface carried by the bimetallic strip and adapted for engagement with a cooperating element l of the operating means, a magnetic armature disposed adjacent to and in normally spaced relationship from a portion of said core, said Ibimetallic strip being adapted upon flexing to shift the latching surface in the direction of bimetallic exure to release said operating means, the magnetic core and armature cooperating when energized to pivot the bimetallic strip and support member about the abutment members to shift the latching surface in a direction transverse to the direction of bimetallic exure and effect release of the operating means.

11. In a circuit breaker comprising a housing, movable contacts disposed within the housing, and spring urged operating means for opening and closing said contacts, the improvement which comprises current responsive tripping means effective to releasably latch the operating means and to release the operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a support plate, one end of said bimetallic strip being mounted upon the upper surface of said support plate, stationary abutment members in engagement with said support member, the undersurface of said plate including a central longitudinal groove and a transverse groove, a compression spring engaging the lower surface of said support plate and urging said plate into engagement with said abutment members, said spring including a diametral segment disposed within said longitudinal groove and a second segment in engagement with said transverse groove, said abutment members and spring cooperating to hold said support plate stationary during flexure of said bimetallic strip but permitting pivotal movement of said support plate in a plane transverse to the plane of ilexure of said bimetallic strip, the second segment of said spring tending to resist said pivotal movement, a magnetic core mounted on the free end of the bimetallic strip, a latching surface carried by the bimetallic strip and adapted for engagement with a cooperating element of the operating means, a magnetic armature disposed adjacent to and in normally spaced relationship Ifrom a portion of said core, said bimetallic strip being adapted upon flexing to shift the latching sur- 12 face in the direction of bimetallic fiexure to release said operating means, the magnetic core and armature cooperating when energized to pivot the bimetallic strip and support plate about the abutment members to shift the latching surface in a direction transverse to the direction of bimetallic eXure and effect release of the operating means.

l2. In a circuit breaker comprising a housing, movable contacts disposed within the housing, and spring urged operating means for opening and closing said contacts, the improvement which comprises current responsive tripping means effective to releasably latch the operating means and to release the operating means in response to an over load current, said tripping means comprising an elongated bimetallic strip, a support member, one end of said bimetallic strip being mounted upon said support member, a compression spring engaging the opposite side of said support member from said bimetallic strip, stationary abutment members in engagement with said support member, said abutment members and spring cooperating to hold said support member stationary during flexure of said bimetallic strip but permitting pivotal movement of said support member in a plane transverse to the plane of fiexure of said bimetallic strip, a U-shaped magnetic core mounted on the free end of the bimetallic strip, said core including two spaced arms and a projecting latching surface adapted for engagement with a cooperating element of the operating means, a magnetic armature pivotally carried by one arm of the armature and including a section disposed adjacent to and in normally spaced relationship from the second arm of said core, said armature including an arm extending at an angle to said section and adapted to engage said housing, said bimetallic strip being adapted upon flexing to shift the latching surface in the direction of bimetallic exure to release said operating means, the magnetic core being effective when energized to attract said armature toward the second arm of the core whereby the armature forces the bimetallic strip and support member to pivot about the abutment members to shift the latching surface in a direction transverse to the direction of bimetallic exure and thereby etect release of the operating means.

13. In a circuit breaker comprising a housing, movable contacts disposed within the housing, and spring urged operating means for opening and closing said contacts, the improvement which comprises current responsive tripping means effective to releasably latch the operating means and to release the operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a support member, one end of said bimetallic strip being mounted upon said support member, a compression spring engaging the opposite side of said support member from said bimetallic strip, stationary abutment members in engagement with said support member, said abutment members and spring cooperating to hold said support member stationary during fiexure of said bimetallic strip but permitting pivotal movement of said support member in a plane transverse to the plane of iiexure of said bimetallic strip, a U-shaped magnetic core mounted on the free end of the bimetallic strip, said core including two spaced arms and a latching surface for engagement with a cooperating element of the operating means, said arms extending transverse to the direction of bimetal flexure, a magnetic armature mounted in said housing adjacent to and in normally spaced relationship from the arms of said core, said bimetallic strip being adapted upon flexing to shift the latching surface in the direction of bimetallic eXure to release said operating means, the magnetic core when energized being attracted to said armature, whereby the bimetallic strip and support member pivot about the abutment members to shift the latching surface in a direction transverse to the direction of bimetallic exure and effect release of the operating means.

14. In a circuit breaker comprising a housing, movable contacts disposed within the housing, and spring urged operating means for opening and closing said contacts, the improvement which comprises current responsive tripping means eifective to releasably latch the operating means and to release the operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a support member, one end of said bimetallic strip being mounted upon said support member, a compression spring engaging the oppositeside of said support member from said bimetallic strip, stationary abutment members in engagement with said support member, said abutment members and spring cooperating to hold said mounting member stationary during flexure of said bimetallic strip but permitting pivotal movement of said support member in a plane transverse to the plane of liexure of said bimetallic strip, a U-shaped magnetic core mounted on the free end of the bimetallic strip,`said core comprising two spaced arms, a latching surface carried by the bimetallic strip and adapted for engagement with a cooperating element of the operating means, a magnetic armature pivotally mounted upon one arm of the core in normally spaced relationship from the other arm of said core, abutment means for preventing movement of the armature toward said last named arm, said bimetallic strip being adapted upon exing to shift the latching surface in the direction of bimetallic flexure to release said operating means, the magnetic core attracting said armature when energized to pivot the bimetallic strip and support member about the abutment members to shift the latching surface in a direction transverse to the direction of bimetallic ilexure and eect release of the operating means.

15. In a circuit breaker comprising a housing, movable contacts disposed within the housing, and spring urged operating means for opening and closing said contacts, the improvement which comprises current responsive tripping means effective to releasably latch the operating means and to release the operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a support member, one end of said bimetallic strip being mounted upon said support member, a compression spring engaging the opposite side of said support member from said bimetallic strip, stationary abutment means in engagement with said support member, said abutment means and spring cooperating to hold said support member stationary during fleXure of said bimetallic strip but permitting pivotal movement of said support member in a plane transverse to the plane of flexure of said vbimetallic strip, a U-shaped magnetic core mounted on the free end of the bimetallic strip, said core having two spaced arms extending transverse to the plane of bimetallic fleXure, a latching surface carried by the bimetallic strip and adapted for engagement with a cooperating element of the operating means, a magnetic armature pivotally supported by one of said core arms and disposed adjacent to and in normally spaced relationship from the second of said core arms, an abutment surface on said housing for preventing movement of said armature toward said second arm, said bimetallic strip being adapted upon flexing to shift the latching surface in the direction of bimetallic flexure to release said operating means, the magnetic core and armature cooperating when energized to pivot the bimetallic strip and support member about the abutment means to shift the latching surface in a direction transverse to the direction of bimetallic exure and effect release of the operating means.

16. In a circuit breaker comprising a housing, movable contacts disposed Within the housing and spring urged operating means for opening and closing said contacts, the improvement which comprises current responsive tripping means effective to releasably latch the operating means and to release the operating means in response to an overload current, said tripping means comprising an elongated bimetallic strip, a support member including an upstanding arm having a groove formed therein, one end of said bimetallic strip being mounted upon said support member, a spring engaging the opposite side of said support member from said bimetallic strip, an abutment member in engagement with a portion of said support member remote from said arm, a tapered Calibrating screw in engagement with said notch, said abutment member, screw and spring cooperating to hold said support member stationary during fleXure of said bimetallic strip but permitting pivotal movement of said support member in a plane transverse to the plane of ileXure of said bimetallic strip, a magnetic core mounted on the free end of the bimetallic strip, a second adjustably positioned Calibrating screw in abutment with said core and adapted to shift said core transversely of the plane of bimetallic flexure, a latching surface carried by the bimetallic strip and adapted for engagement with a cooperating element of the operating means, a magnetic armature disposed adjacent to and in normally spaced relationship from a portion of said core, said bimetallic strip being adapted upon flexing to shift the latching surface in the direction of bimetallic fleXure to release said operating means, the magnetic core and armature cooperating when energized to pivot the bimetallic strip and support member about the abutment member and Calibrating screw to shift the latching surface in a direction transverse to the direction of bimetallic eXure and eiect release of the operating means.

17. In a circuit breaker comprising a housing, relatively movable contacts disposed within said housing, spring urged operating means for opening said contacts, current responsive tripping means effective to releasably latch said operating means and to release said operating means in response to an overload current, the improvement which comprises a magnetically permeable core member adapted to cooperate with a magnetic armature for tripping said breaker upon the occurrence of a heavy overload condition, said core comprising an over folded strip of ferro magnetic material, said strip being of substantially U-shaped configuration comprising two spaced arms and an interconnecting segment, each of said arms and said segment including two adjacent layers of ferro magnetic material.

18. In a circuit breaker comprising a housing, relatively movable contacts disposed within said housing, spring urged operating means for opening said contacts, current responsive tripping means effective to releasably latch said operating means and to release said operating means in response to an overload current, the improvement which comprises a magnetically permeable core member adapted to cooperate with a magnetic armature for tripping said breaker upon the occurrence of a heavy overload condition, said core comprising an over foldedv strip of ferro magnetic material, said strip being of substantially U-shaped configuration comprising two spaced arms and an interconnecting segment, each of said arms and said segment including two adjacent layers of ferro magnetic material, one layer of said connecting segment being bent outwardly to form a latching surface adapted for cooperative engagement with the operating means.

References Cited in the le of this patent UNITED STATES PATENTS 

